POV bike wheels with the MSP430

Being an intern a Texas Instruments isn’t all fun and games, but from [George], [Valerie], and [Ryan]’s TI intern design project, it sure looks like it. They built a persistence of vision display for a bicycle using the ever popular MSP430 Launchpad board.

The team of interns created a POV display by combining the power of the TI Launchpad with a row of 32 RGB LEDs soldered onto a booster pack. Once the whole circuit is fastened securely to the bike wheel, a hall effect sensor mounted to the bike frame allows the MSP430 to detect how fast it is going. From there, it’s just a matter of flashing LEDs at the right time to create a stationary display inside a rotating wheel.

Although the display will theoretically work with just one Launchpad/Booster pack combo, the team decided to use three of these circuits, totaling 96 LEDs per wheel, to create a really nice RGB display. The video (available after the break) shows a little bit of flicker but this is an artifact of the camera. In real life, the POV bike wheel display is simply stunning.

There is PWM. Since there were only 5 weeks and we have very low quality LEDs, we were not sure how much color difference people would actually be able to see if between say 230 Red and 255 Red. Some of those in the video are not maximized, so they are variable colors ranging from 0-255.

Just a word of advice, you can power the LEDs with an unregulated voltage when driving them with a constant current driver like the TLC5940. Also your regulator is rate at 500mA, but you have 32RGB LEDs on that board, and a 2.2K resistor should set the current around 10mA for each LED. So if you turn everything on full blast your LEDs would be drawing a total of 960mA. The regulator will probably survive, but it’ll reset itself and the attached MSP430.